In satellite communication, a terrestrial station may monitor a received power and quality of a satellite downlink signal, for estimating the quality of the signal path between it and the satellite. The terrestrial station can use the estimate to adjust the power of its uplink signal to the satellite, enabling the satellite to receive the signal at a steady power level, irrespective of changing conditions of the signal path.
One technique for terrestrial station monitoring of downlink signal quality includes the satellite transmitting a Continuous Waveform (CW) pilot signal with the downlink. The CW pilot signal is easily recovered and analyzed at the terrestrial station. However, the CW pilot signal technique can have technical problems. One is that a CW signal is narrowband, and therefore, transmission sufficient for reliable reception at the terrestrial station can produce a high power spectral density. The high power density can create significant technical problems, e.g., interference of other communication channels, and practical problems, namely, regulatory limits on spectral power density.
Another technique for terrestrial station monitoring of downlink signal quality includes the station recovering the downlink symbol stream and estimating the signal quality from characteristics of that stream. However, this technique can have significant resource costs because the downlink signal can use complex modulation, in addition to being heavily encoded for error correction and being encrypted. Moreover, there can be applications requiring terrestrial station monitoring of downlink signal quality, without need for the information carried by the recovered symbols. In such applications, the resource cost of the symbol stream recovery can be an undesirable overhead.
Accordingly, there exists a technical need for low complexity, low cost, rapid, and accurate estimation of received signal power and quality.